1 /* 2 * Pid namespaces 3 * 4 * Authors: 5 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc. 6 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM 7 * Many thanks to Oleg Nesterov for comments and help 8 * 9 */ 10 11 #include <linux/pid.h> 12 #include <linux/pid_namespace.h> 13 #include <linux/user_namespace.h> 14 #include <linux/syscalls.h> 15 #include <linux/err.h> 16 #include <linux/acct.h> 17 #include <linux/slab.h> 18 #include <linux/proc_fs.h> 19 #include <linux/reboot.h> 20 #include <linux/export.h> 21 22 #define BITS_PER_PAGE (PAGE_SIZE*8) 23 24 struct pid_cache { 25 int nr_ids; 26 char name[16]; 27 struct kmem_cache *cachep; 28 struct list_head list; 29 }; 30 31 static LIST_HEAD(pid_caches_lh); 32 static DEFINE_MUTEX(pid_caches_mutex); 33 static struct kmem_cache *pid_ns_cachep; 34 35 /* 36 * creates the kmem cache to allocate pids from. 37 * @nr_ids: the number of numerical ids this pid will have to carry 38 */ 39 40 static struct kmem_cache *create_pid_cachep(int nr_ids) 41 { 42 struct pid_cache *pcache; 43 struct kmem_cache *cachep; 44 45 mutex_lock(&pid_caches_mutex); 46 list_for_each_entry(pcache, &pid_caches_lh, list) 47 if (pcache->nr_ids == nr_ids) 48 goto out; 49 50 pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL); 51 if (pcache == NULL) 52 goto err_alloc; 53 54 snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids); 55 cachep = kmem_cache_create(pcache->name, 56 sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid), 57 0, SLAB_HWCACHE_ALIGN, NULL); 58 if (cachep == NULL) 59 goto err_cachep; 60 61 pcache->nr_ids = nr_ids; 62 pcache->cachep = cachep; 63 list_add(&pcache->list, &pid_caches_lh); 64 out: 65 mutex_unlock(&pid_caches_mutex); 66 return pcache->cachep; 67 68 err_cachep: 69 kfree(pcache); 70 err_alloc: 71 mutex_unlock(&pid_caches_mutex); 72 return NULL; 73 } 74 75 static void proc_cleanup_work(struct work_struct *work) 76 { 77 struct pid_namespace *ns = container_of(work, struct pid_namespace, proc_work); 78 pid_ns_release_proc(ns); 79 } 80 81 /* MAX_PID_NS_LEVEL is needed for limiting size of 'struct pid' */ 82 #define MAX_PID_NS_LEVEL 32 83 84 static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns, 85 struct pid_namespace *parent_pid_ns) 86 { 87 struct pid_namespace *ns; 88 unsigned int level = parent_pid_ns->level + 1; 89 int i; 90 int err; 91 92 if (level > MAX_PID_NS_LEVEL) { 93 err = -EINVAL; 94 goto out; 95 } 96 97 err = -ENOMEM; 98 ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); 99 if (ns == NULL) 100 goto out; 101 102 ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL); 103 if (!ns->pidmap[0].page) 104 goto out_free; 105 106 ns->pid_cachep = create_pid_cachep(level + 1); 107 if (ns->pid_cachep == NULL) 108 goto out_free_map; 109 110 kref_init(&ns->kref); 111 ns->level = level; 112 ns->parent = get_pid_ns(parent_pid_ns); 113 ns->user_ns = get_user_ns(user_ns); 114 INIT_WORK(&ns->proc_work, proc_cleanup_work); 115 116 set_bit(0, ns->pidmap[0].page); 117 atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1); 118 119 for (i = 1; i < PIDMAP_ENTRIES; i++) 120 atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE); 121 122 return ns; 123 124 out_free_map: 125 kfree(ns->pidmap[0].page); 126 out_free: 127 kmem_cache_free(pid_ns_cachep, ns); 128 out: 129 return ERR_PTR(err); 130 } 131 132 static void destroy_pid_namespace(struct pid_namespace *ns) 133 { 134 int i; 135 136 for (i = 0; i < PIDMAP_ENTRIES; i++) 137 kfree(ns->pidmap[i].page); 138 put_user_ns(ns->user_ns); 139 kmem_cache_free(pid_ns_cachep, ns); 140 } 141 142 struct pid_namespace *copy_pid_ns(unsigned long flags, 143 struct user_namespace *user_ns, struct pid_namespace *old_ns) 144 { 145 if (!(flags & CLONE_NEWPID)) 146 return get_pid_ns(old_ns); 147 if (flags & (CLONE_THREAD|CLONE_PARENT)) 148 return ERR_PTR(-EINVAL); 149 if (task_active_pid_ns(current) != old_ns) 150 return ERR_PTR(-EINVAL); 151 return create_pid_namespace(user_ns, old_ns); 152 } 153 154 static void free_pid_ns(struct kref *kref) 155 { 156 struct pid_namespace *ns; 157 158 ns = container_of(kref, struct pid_namespace, kref); 159 destroy_pid_namespace(ns); 160 } 161 162 void put_pid_ns(struct pid_namespace *ns) 163 { 164 struct pid_namespace *parent; 165 166 while (ns != &init_pid_ns) { 167 parent = ns->parent; 168 if (!kref_put(&ns->kref, free_pid_ns)) 169 break; 170 ns = parent; 171 } 172 } 173 EXPORT_SYMBOL_GPL(put_pid_ns); 174 175 void zap_pid_ns_processes(struct pid_namespace *pid_ns) 176 { 177 int nr; 178 int rc; 179 struct task_struct *task, *me = current; 180 181 /* Ignore SIGCHLD causing any terminated children to autoreap */ 182 spin_lock_irq(&me->sighand->siglock); 183 me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; 184 spin_unlock_irq(&me->sighand->siglock); 185 186 /* 187 * The last thread in the cgroup-init thread group is terminating. 188 * Find remaining pid_ts in the namespace, signal and wait for them 189 * to exit. 190 * 191 * Note: This signals each threads in the namespace - even those that 192 * belong to the same thread group, To avoid this, we would have 193 * to walk the entire tasklist looking a processes in this 194 * namespace, but that could be unnecessarily expensive if the 195 * pid namespace has just a few processes. Or we need to 196 * maintain a tasklist for each pid namespace. 197 * 198 */ 199 read_lock(&tasklist_lock); 200 nr = next_pidmap(pid_ns, 1); 201 while (nr > 0) { 202 rcu_read_lock(); 203 204 task = pid_task(find_vpid(nr), PIDTYPE_PID); 205 if (task && !__fatal_signal_pending(task)) 206 send_sig_info(SIGKILL, SEND_SIG_FORCED, task); 207 208 rcu_read_unlock(); 209 210 nr = next_pidmap(pid_ns, nr); 211 } 212 read_unlock(&tasklist_lock); 213 214 /* Firstly reap the EXIT_ZOMBIE children we may have. */ 215 do { 216 clear_thread_flag(TIF_SIGPENDING); 217 rc = sys_wait4(-1, NULL, __WALL, NULL); 218 } while (rc != -ECHILD); 219 220 /* 221 * sys_wait4() above can't reap the TASK_DEAD children. 222 * Make sure they all go away, see free_pid(). 223 */ 224 for (;;) { 225 set_current_state(TASK_UNINTERRUPTIBLE); 226 if (pid_ns->nr_hashed == 1) 227 break; 228 schedule(); 229 } 230 __set_current_state(TASK_RUNNING); 231 232 if (pid_ns->reboot) 233 current->signal->group_exit_code = pid_ns->reboot; 234 235 acct_exit_ns(pid_ns); 236 return; 237 } 238 239 #ifdef CONFIG_CHECKPOINT_RESTORE 240 static int pid_ns_ctl_handler(struct ctl_table *table, int write, 241 void __user *buffer, size_t *lenp, loff_t *ppos) 242 { 243 struct pid_namespace *pid_ns = task_active_pid_ns(current); 244 struct ctl_table tmp = *table; 245 246 if (write && !ns_capable(pid_ns->user_ns, CAP_SYS_ADMIN)) 247 return -EPERM; 248 249 /* 250 * Writing directly to ns' last_pid field is OK, since this field 251 * is volatile in a living namespace anyway and a code writing to 252 * it should synchronize its usage with external means. 253 */ 254 255 tmp.data = &pid_ns->last_pid; 256 return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); 257 } 258 259 extern int pid_max; 260 static int zero = 0; 261 static struct ctl_table pid_ns_ctl_table[] = { 262 { 263 .procname = "ns_last_pid", 264 .maxlen = sizeof(int), 265 .mode = 0666, /* permissions are checked in the handler */ 266 .proc_handler = pid_ns_ctl_handler, 267 .extra1 = &zero, 268 .extra2 = &pid_max, 269 }, 270 { } 271 }; 272 static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; 273 #endif /* CONFIG_CHECKPOINT_RESTORE */ 274 275 int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) 276 { 277 if (pid_ns == &init_pid_ns) 278 return 0; 279 280 switch (cmd) { 281 case LINUX_REBOOT_CMD_RESTART2: 282 case LINUX_REBOOT_CMD_RESTART: 283 pid_ns->reboot = SIGHUP; 284 break; 285 286 case LINUX_REBOOT_CMD_POWER_OFF: 287 case LINUX_REBOOT_CMD_HALT: 288 pid_ns->reboot = SIGINT; 289 break; 290 default: 291 return -EINVAL; 292 } 293 294 read_lock(&tasklist_lock); 295 force_sig(SIGKILL, pid_ns->child_reaper); 296 read_unlock(&tasklist_lock); 297 298 do_exit(0); 299 300 /* Not reached */ 301 return 0; 302 } 303 304 static __init int pid_namespaces_init(void) 305 { 306 pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); 307 308 #ifdef CONFIG_CHECKPOINT_RESTORE 309 register_sysctl_paths(kern_path, pid_ns_ctl_table); 310 #endif 311 return 0; 312 } 313 314 __initcall(pid_namespaces_init); 315